Middle East respiratory syndrome coronavirus infection causes

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: João André Alves Silva, M.D. [2]

Overview

Ten years after the outbreak of SARS-CoV, the MERS-CoV is identified as the agent of a lethal pneumonia in patients who have recently been related to the Arabian Peninsula. The Middle east respiratory syndrome coronavirus (MERS-CoV), also termed EMC/2012 (HCoV-EMC/2012), is positive-sense, single-stranded RNA novel species of the genus Betacoronavirus.[1][2] First called novel coronavirus 2012 or simply novel coronavirus, it was first reported in 2012 after genome sequencing of the virus, isolated from sputum samples of patients, affected by a 2012 outbreak of a "new flu". Until May 2013, MERS-CoV was being described as a SARS-like virus or colloquially as "Saudi SARS. Since then it is known to be distinct, not only from SARS-CoV, but also from other known endemic coronaviruses, such as betacoronavirus HCoV-OC43 and HCoV-HKU1, as well as from the common cold coronavirus.[3] As of May 2014, several MERS-CoV cases have been reported in different countries, including Saudi Arabia, Malaysia, Jordan, Qatar, Egypt, the United Arab Emirates, Tunisia, Kuwait, Oman, Algeria, Bangladesh, the United Kingdom and the United States.[4]

Causes

This negatively-stained transmission electron micrograph revealed ultrastructural morphology of the Middle East Respiratory Syndrome Coronavirus (MERS-CoV). Courtesy: Public Health Image Library (PHIL), Centers for Disease Control and Prevention (CDC)[5]
This highly-magnified negatively-stained transmission electron micrograph revealed ultrastructural morphology of the Middle East Respiratory Syndrome Coronavirus (MERS-CoV). Courtesy: Public Health Image Library (PHIL), Centers for Disease Control and Prevention (CDC)[6]
This thin section transmission electron micrograph revealed ultrastructural morphology of the Middle East Respiratory Syndrome Coronavirus (MERS-CoV). Courtesy: Public Health Image Library (PHIL), Centers for Disease Control and Prevention (CDC)[7]
This highly-magnified transmission electron micrograph revealed the presence of numerous Middle East Respiratory Syndrome Coronavirus (MERS-CoV) virions in this tissue culture sample. Courtesy: Public Health Image Library (PHIL), Centers for Disease Control and Prevention (CDC)[8]
This highly-magnified transmission electron micrograph revealed the presence of numerous Middle East Respiratory Syndrome Coronavirus (MERS-CoV) virions in this tissue culture sample. Courtesy: Public Health Image Library (PHIL), Centers for Disease Control and Prevention (CDC)[9]

MERS-CoV is caused by a lineage C betacoronavirus.

Taxonomy

Betacoronavirus is an enveloped, spherical (120 nm in diameter), single-stranded, positive-strand RNA virus that belongs to the family Coronaviridae of the order Nidovirales.

Genome

The betacoronavirus contains a genome composed of 30,119 nucleotides that encodes structural and non-structural proteins. The genome is considered the largest among all RNA virus genomes, reaching 27-32 kb in size.

Tropism

Transmission

  • MERS-CoV is thought to have a zoonotic activity, whereby transmission may occur from animals to humans. Bats are the natural host of the betacoronavirus, but it is unknown if MERS coronavirus transmission to humans is through bats, through an intermediate animal hosts following crossover and subsequent adaptation, or through a completely different host.
  • Limited data is available to confirm or rule out human-to-human transmission.

Since may 29th 2013, the WHO has warned that the MERS-CoV should be considered a "threat to the entire world".[2] Transmission of MERS-CoV is prone to occur in immunocompromised patients, or in patients with other comorbidities, such as diabetes or renal failure.[2] In a study of 23 patients of the largest outbreak so far, in Saudi Arabia, was determined that 74% had underlying diabetes mellitus, 52% renal disease and 43% lung disease, highlighting the impact of underlying comorbidities in the overall risk of infection with MERS-CoV. This evidence is further supported by the fact that cases of infected family members and health-care workers was only reported in 1 to 2% of contacts.[2][10]

At the present time it is not known the stage at which an infected MERS-CoV patient becomes contagious, if he is able to transmit the virus while there is still no evidence respiratory illness, or if there is transmission only after symptom onset. If the first is correct, then the the control of a larger outbreak will be more challenging, considering the prevalence of global traveling nowadays.[2]

One of the major gaps of knowledge about this virus is that its prevalence in the community is not known, therefore, and since most of the identified cases were patients with underlying comorbidities, there is a possibility of MERS-CoV to be a common infection in Saudi-Arabia, with which patients without these comorbidties only develop minor respiratory symptoms or are asymptomatic.[2]

Natural Reservoir

In contrast to the SARS-CoV, that in its outbreak back in 2002/2003 had adapted so much to the human population that it could no longer infect bat cells, the MERS-CoV is able to infect both animal and human cells. This fact suggests the existence of a possible bat to human transmission.[11] However, considering the low probability of every infected human having been in contact with bats, it is more likely that another animal host, common in the Arabian Peninsula such as goats or camels, was the source for the infection. This is supported by the discovery of neutralizing antibodies for MERS-CoV in all dromedary camels of Oman, as well as by the full-genome sequence of MERS-CoV from dromedaries that was revealed to be 99.9% similar with the genome of human clade B of MERS-CoV. A further study on dromedary camels from Saudi Arabia, published in December 2013, revealed the presence of MERS-CoV in 90% of the evaluated dromedary camels, suggesting that dromedary camels not only could be the main reservoir of MERS-CoV, but also the animal origin of MERS. This discoveries are of extreme relevance since they allow the definition of the human populations at risk, so that further protective measures might be taken.[12][13][14] According to the March 2014 MERS-CoV summary update from the WHO, recent studies claim that camels serve as the primary source of the MERS-CoV infection in humans, while bats may be the ultimate reservoir of the virus. Evidence includes the frequency with which the virus has been found in camels, to which human cases have been exposed, seriological data which shows widespread transmission in camels and the similarity of the camel coronavirus to the human type.[15]

Gallery

References

  1. ↑ De Groot RJ; et al. (15 May 2013). "Middle East Respiratory Syndrome Coronavirus (MERS-CoV): Announcement of the Coronavirus Study Group". Journal of Virology. 87 (14): 7790–2. doi:10.1128/JVI.01244-13. PMC 3700179. PMID 23678167.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 Perlman, S. (2013). "The Middle East Respiratory Syndrome--How Worried Should We Be?". mBio. 4 (4): e00531–13–e00531–13. doi:10.1128/mBio.00531-13. ISSN 2150-7511.
  3. ↑ Saey, Tina Hesman (27 February 2013). "Scientists race to understand deadly new virus: SARS-like infection causes severe illness, but may not spread quickly". Science News. 183 (6). p. 5.
  4. ↑ "Patient with deadly MERS virus waited hours in Florida ER". 2014-05-14. Retrieved 2014-05-14.
  5. ↑ "http://phil.cdc.gov/phil/details.asp". External link in |title= (help)
  6. ↑ "http://phil.cdc.gov/phil/details.asp". External link in |title= (help)
  7. ↑ "http://phil.cdc.gov/phil/details.asp". External link in |title= (help)
  8. ↑ "http://phil.cdc.gov/phil/details.asp". External link in |title= (help)
  9. ↑ "http://phil.cdc.gov/phil/details.asp". External link in |title= (help)
  10. ↑ Assiri, Abdullah; McGeer, Allison; Perl, Trish M.; Price, Connie S.; Al Rabeeah, Abdullah A.; Cummings, Derek A.T.; Alabdullatif, Zaki N.; Assad, Maher; Almulhim, Abdulmohsen; Makhdoom, Hatem; Madani, Hossam; Alhakeem, Rafat; Al-Tawfiq, Jaffar A.; Cotten, Matthew; Watson, Simon J.; Kellam, Paul; Zumla, Alimuddin I.; Memish, Ziad A. (2013). "Hospital Outbreak of Middle East Respiratory Syndrome Coronavirus". New England Journal of Medicine. 369 (5): 407–416. doi:10.1056/NEJMoa1306742. ISSN 0028-4793.
  11. ↑ Muller, M. A.; Raj, V. S.; Muth, D.; Meyer, B.; Kallies, S.; Smits, S. L.; Wollny, R.; Bestebroer, T. M.; Specht, S.; Suliman, T.; Zimmermann, K.; Binger, T.; Eckerle, I.; Tschapka, M.; Zaki, A. M.; Osterhaus, A. D. M. E.; Fouchier, R. A. M.; Haagmans, B. L.; Drosten, C. (2012). "Human Coronavirus EMC Does Not Require the SARS-Coronavirus Receptor and Maintains Broad Replicative Capability in Mammalian Cell Lines". mBio. 3 (6): e00515–12–e00515–12. doi:10.1128/mBio.00515-12. ISSN 2150-7511.
  12. ↑ Reusken, Chantal BEM; Haagmans, Bart L; Müller, Marcel A; Gutierrez, Carlos; Godeke, Gert-Jan; Meyer, Benjamin; Muth, Doreen; Raj, V Stalin; Vries, Laura Smits-De; Corman, Victor M; Drexler, Jan-Felix; Smits, Saskia L; El Tahir, Yasmin E; De Sousa, Rita; van Beek, Janko; Nowotny, Norbert; van Maanen, Kees; Hidalgo-Hermoso, Ezequiel; Bosch, Berend-Jan; Rottier, Peter; Osterhaus, Albert; Gortázar-Schmidt, Christian; Drosten, Christian; Koopmans, Marion PG (2013). "Middle East respiratory syndrome coronavirus neutralising serum antibodies in dromedary camels: a comparative serological study". The Lancet Infectious Diseases. 13 (10): 859–866. doi:10.1016/S1473-3099(13)70164-6. ISSN 1473-3099.
  13. ↑ Hemida first=Maged G; Chu, Daniel KW; Poon, Ranawaka; Perera, Mohammad A A; Ng, Hoiyee-Y (Jul 2014). "MERS coronavirus in dromedary camel herd, Saudi Arabia". Retrieved 22 Apr 2014. The full-genome sequence of MERS-CoV from dromedaries in this study is 99.9% similar to genomes of human clade B MERS-CoV.
  14. ↑ Hemida, MG (2013). "Middle East Respiratory Syndrome (MERS) coronavirus seroprevalence in domestic livestock in Saudi Arabia, 2010 to 2013". Euro Surveillance. 18 (50).
  15. ↑ "Middle East respiratory syndrome coronavirus (MERS‐CoV)Summary and literature update – as of 27 March2014" (PDF). 27 Mar 2014. Retrieved 24 Apr 2014.
  16. ↑ 16.00 16.01 16.02 16.03 16.04 16.05 16.06 16.07 16.08 16.09 16.10 16.11 16.12 "Public Health Image Library (PHIL)".

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